You would be surprised at what the government has in well populated cities.
Even in Austin...ever drive around near the center of our city, around the State Capital, and ever notice all the VERY lightly or even UN-marked government buildings in that 5 block area? How about on Lamar where the State and Federal Departments of Health buildings are?
Hell, most people never knew that the IRS and FBI had field offices in the building on MOPAC and 183 that the nutjob flew his plane into...along with a FEMA office, and a HUD office.
I'm not trying to go all tin-foil hat here (I can't stand conspiracy theorists), but having worked for the government/military, you kinda learn how they hide things....IN PLAIN SIGHT!